I have moaned and groaned about a chip problem with my Jet planer for half a decade. When I first bought the machine I didn't have this problem. After I got the knives sharpened for the first time I did. And ever since that I have had a problem with chips coming around with the cutter-head and leaving marks in my wood, and chips getting crushed into my wood by the rollers.
I recently flipped over the orange plastic chip guide, put the bevel down. This allows the chip guide to be pushed forward a little more than before. This eliminated about 10% of my problem.
I had some free time to blow while waiting for someone to show up. I was told time and time again it was my vacuum system. So I was feeling around with my hand while the vacuum was on (machine off) and noticing how much vacuum was around the cutter-head. I also noticed while I was planing that the problematic chips would come from in front of the last outfeed roller, in between the roller and the casting. I felt for vacuum in that area and there was essentially none. I wondered why. I pulled the guards off, and there is no way for any vacuum to get to that area. So I made it so it could. I drilled a series of nine 9/16" holes in the casting, spaced apart 1 1/4". Now I didn't have a lot of vacuum there, but there was some. It seems to be enough to keep the chips from falling down to the board.
I have only run a test board through it. On fast speeds, taking 1/8" off an 8" wide poplar board, I got no chip fall. I still had a few chips being beat by the cutterhead, but very little compared to what I usually get.
So, it may not be a perfect fix, and I might make the holes bigger or even connect them to make a slot. But it is a start, and is actually making a big difference. Here are some pictures with the top guard off.
(Solid Wood Machining Forum)
From contributor S:
Thanks for the update. I think you just saved me a lot of heartache.
I added 8 more holes, in between the others. After I put a 13" board through on high speed at 3/32", I had some chip fallout on the board. The vacuum is very strong in that area between the roller and the casting. Works even better now. I have also moved the plastic orange chip deflector back some so the noise is reduced with the vacuum on.
Typically they are pulling the chips out the back through a 4" hole with no real plenum. The chips have to travel 270 degrees around the cutter head to hopefully be picked up by the unfocused suction. Ideally you want to suck out the top of the planer through a true plenum. Maybe 1 1/2" wide by the length of the cutterhead. I threw away the stock plenum on my 18" Woodmaster and installed a top mounted plenum like I described with a 6" duct. It was a slightly modified floor sweep duct. I've had 99% suction on the planer for the last decade.
My last boss didn't cut a hole through the top of our huge SCMI planer because of resale value (we talked about it numerous times). That monster clogged constantly. Nice to see you've made progress on your machine.